We have established the direct relationship between the analysis of the protein content of dental plaque samples and the dry weight of the samples. We have quantitated very small dental plaque samples by applying methods of analysis which have been developed in this laboratory. We have also quantitated dental plaque samples by the extraction and analysis of flavin mononucleotide (FMN). The FMN analysis to quantitate plaque can be performed in the presence of protein or amine containing materials. The specific FMN content of dental plaque samples was constant for both pooled plaque samples and for small samples obtained from individual teeth. The minimum sample size for a constant specific FMN content of dental plaque was 30 micrograms dry weight. Attempts have continued to normalize the plaque samples using unique bacterial constituents such as D-alanine and muramic acid. The analysis of the visible fraction of the dental plaque mass has continued with attempts to establish the relationship of "adenylate energy charge" (AEC) to the percent viable cells in a population.